Coating solution, and gas barrier film, gas barrier laminate and gas barrier multilayer film, using the coating solution, and their manufacturing methods

ABSTRACT

A coating solution comprising:
         a first solvent;   0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent;   0.01 to 0.35 chemical equivalent of an alkali metal compound relative to an amount of carboxyl group in the polycarboxylic acid-based polymer; and   0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group,   wherein a number average molecular weight of the polycarboxylic acid-based polymer is in a range of 40,000 to 10,000,000.

TECHNICAL FIELD

The present invention relates to a gas barrier film, a gas barrier laminate and a gas barrier multilayer film useful as packaging materials of foods, beverages, chemicals, medicines and precision metal components such as electronic components, which tend to degrade due to the effect of oxygen or the like, and packaging materials of articles that need processing (heat sterilization), such as boiling and retort sterilization, under high-temperature hot water conditions, and relates to their manufacturing methods, as well as a coating solution used for their manufacturing methods.

BACKGROUND OF THE INVENTION

Conventionally, polymers that contain a high hydrogen bonding group with high hydrophilicity in their molecules, represented by poly(meth)acrylic acid and polyvinyl alcohol are used as gas barrier polymers. However, while exhibiting very excellent gas barrier properties against oxygen and the like under dry conditions, films made up of only any one of these polymers pose, under a high moisture conditions, problems that their gas barrier properties against oxygen and the like are greatly decreased due to their hydrophilicity, and that the films exhibit inferior resistance against humidity and hot water.

To solve these problems, for example, International Publication No. WO03/091317 (Document 1) discloses a film that uses a polycarboxylic acid-based polymer and a multivalent metal compound as starting materials and has a peak ratio (A1560/A1700) of the infrared absorption spectra of 0.25 or higher. The specification describes a technique involving forming a laminate in which a layer made of a polycarboxylic acid-based polymer and a layer made of a multivalent metal compound are adjacent to each other, and then crosslinking the polycarboxylic acid-based polymer with the multivalent metal.

In addition, as a technique related to the above-described technique, for example, Japanese Unexamined Patent Application Publication No. 2005-125693 (Document 2) discloses a gas barrier laminated film wherein a gas barrier layer made up of a crosslinking substance of a polycarboxylic acid and a multivalent metal compound is formed on at least one side of a film substrate. The specification describes that a substance in which a polycarboxylic acid is partially neutralized with an alkali such as sodium hydroxide, lithium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, barium hydroxide, aluminum hydroxide or ammonia is used as a polycarboxylic acid.

However, it has been found that the gas barrier films described in the above documents and the like, and a package using these films have a problem that their performances are decreased depending on manufacturing processes and applications. That is, whitening may occur or gas barrier properties or transparency may be damaged, in the case of exposure to cold water, for example, the case where an end face part of the film or the package comes into contact with cold water, or is contaminated with attachment of cold water or the case where the package is washed prior to heat sterilization or subjected to immersion treatment, in a process of manufacturing the film or the package.

DISCLOSURE OF THE INVENTION

In consideration of the problems that the above prior art has, the present invention is intended to provide a coating solution for obtaining a packaging material in which whitening can be sufficiently prevented, and also which is excellent in gas barrier properties and transparency, even when a packaging material is exposed to cold water of 30° C. or less, for example, in the case where the packaging material is used for a heat sterilization packaging application or the like. The present invention is also intended to provide a gas barrier film, a gas barrier laminate and a gas barrier multilayer film, using the coating solution, as well as their manufacturing methods.

As a result of intensive studies for accomplishing the above object, the present inventors discovered that, in a packaging material using a coating solution which contains a first solvent, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, 0.01 to 0.35 chemical equivalent of an alkali metal compound relative to the amount of carboxyl group in the polycarboxylic acid-based polymer and 0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group and in which the number average molecular weight of the above polycarboxylic acid-based polymer is in the range of 40,000 to 10,000,000, even in the case where the packaging material is exposed to cold water of 30° C. or lower (for example, exposed to cold water like the case where the end face parts of a film or a package come into contact with cold water, or are contaminated with attachment of cold water or the case where a package is washed prior to heat sterilization or subjected to immersion treatment), a packaging material in which whitening can be sufficiently prevented, and also which is excellent in gas barrier properties and transparency can be obtained, and thereby reaches the completion of the present invention.

A coating solution of the present invention contains a first solvent, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, 0.01 to 0.35 chemical equivalent of an alkali metal compound relative to the amount of carboxyl group in the polycarboxylic acid-based polymer and 0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group, wherein the number average molecular weight of the above polycarboxylic acid-based polymer is in the range of 40,000 to 10,000,000.

A gas barrier film of the present invention comprises a layer (a) formed from a coating solution (A) which contains a first solvent, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, 0.01 to 0.35 chemical equivalent of an alkali metal compound relative to the amount of carboxyl group in the polycarboxylic acid-based polymer, and 0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group, and in which the number average molecular weight of the above polycarboxylic acid-based polymer is in the range of 40,000 to 10,000,000, and a support. The gas barrier film has the layer (a) formed from the coating solution (A) on at least one side of the support.

A gas barrier laminate of the present invention comprises a layer (a) formed from a coating solution (A) which contains a first solvent, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, 0.01 to 0.35 chemical equivalent of an alkali metal compound relative to the amount of carboxyl group in the polycarboxylic acid-based polymer, and 0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group, and in which the number average molecular weight of the above polycarboxylic acid-based polymer is in the range of 40,000 to 10,000,000, a layer (b) formed from a coating solution (B) containing the above multivalent metal compound and a second solvent and a support. The gas barrier laminate has, on at least one side of the support, at least one lamination unit in which the layer (a) formed from the coating solution (A) and the layer (b) formed from the coating solution (B) are adjacent to each other.

Additionally, the gas barrier multilayer film of the present invention comprises the above gas barrier laminate and a plastic film laminated on at least one side of the above gas barrier laminate.

Moreover, the packaging material of the present invention comprises the above gas barrier laminate.

Furthermore, the package of the present invention comprises the above gas barrier laminate.

A method of manufacturing a gas barrier film of the present invention is a method that entails applying, to at least one side of a support, a coating solution (A) which contains a first solvent, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, 0.01 to 0.35 chemical equivalent of an alkali metal compound relative to the amount of carboxyl group in the polycarboxylic acid-based polymer and, 0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group, and in which the number average molecular weight of the above polycarboxylic acid-based polymer is in the range of 40,000 to 10,000,000, followed by drying to obtain a gas barrier film that has the layer (a) formed from the coating solution (A).

A method of manufacturing a gas barrier laminate of the present invention is a method that entails applying, to at least one side of a support, a coating solution (A) which contains a first solvent, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, 0.01 to 0.35 chemical equivalent of an alkali metal compound relative to the amount of carboxyl group in the polycarboxylic acid-based polymer, and 0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group, and in which the number average molecular weight of the above polycarboxylic acid-based polymer is in the range of 40,000 to 10,000,000 and a coating solution (B) containing the above multivalent metal compound and a second solvent, followed by drying to obtain a gas barrier laminate having at least one lamination unit in which the layer (a) formed from the coating solution (A) and the layer (b) formed from the coating solution (B) are adjacent to each other.

A method of manufacturing a gas barrier multilayer film of the present invention is a method that entails applying, to at least one side of a support, a coating solution (A) which contains a first solvent, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, 0.01 to 0.35 chemical equivalent of an alkali metal compound relative to the amount of carboxyl group in the polycarboxylic acid-based polymer, and 0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group, and in which the number average molecular weight of the above polycarboxylic acid-based polymer is in the range of 40,000 to 10,000,000 and a coating solution (B) which contains the above multivalent metal compound and the above second solvent, followed by drying to obtain a gas barrier laminate, and then laminating a plastic film on at least one side of the above barrier laminate to obtain a gas barrier multilayer film.

Here, as for a packaging material using a coating solution of the present invention, it is not known exactly why a packaging material in which whitening can be sufficiently prevented, and also which is excellent in gas barrier properties and transparency, even when the packaging material is exposed to cold water of 30° C. or less. However, the present inventors speculate as follows.

That is, when the packaging material is exposed to water, swelling of a polycarboxylic acid-based polymer and crosslinking caused by a multivalent metal compound progress at the same time. When a packaging material is exposed to cold water, the progress of crosslinking caused by the multivalent metal compound in a layer made up of the polycarboxylic acid-based polymer is slow as compared with the case where, for example, the packaging material is exposed to warm water of 70° C. or higher. Hence, the swelling of the polycarboxylic acid-based polymer progresses preferentially. When the crosslinking caused by the multivalent metal compound in the polycarboxylic acid-based polymer layer is effected after the swelling of the polycarboxylic acid-based polymer preferentially progresses due to the moisture that intrudes to the layer made up of the polycarboxylic acid-based polymer, a uniform layer cannot be kept because of the influence of moisture in the polycarboxylic acid-based polymer layer. The present inventors speculate that whitening occurs or gas barrier properties and the transparency are damaged as a result of the above factors. Then, the present inventors speculate as follows. In a packaging material that uses a coating solution of the present invention, the crosslinking caused by the multivalent metal compound in the polycarboxylic acid layer before the packaging material is exposed to cold water progresses sufficiently and water resistance of the polycarboxylic acid-based polymer layer is improved. Therefore, it is possible to obtain a packaging material in which whitening can be sufficiently prevented, and also which is excellent in gas barrier properties and transparency.

The present invention makes it possible to provide a coating solution for obtaining a packaging material in which whitening can be sufficiently prevented, and also which is excellent in gas barrier properties and transparency, even when the material is exposed to cold water of 30° C., for example, in the case where the packaging material is used for a heat sterilization packaging application or the like. The present invention also makes it possible to provide a gas barrier film, a gas barrier laminate, and a gas barrier multilayer film, using the coating solution, as well as their manufacturing methods.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in detail by means of preferred embodiments.

<Coating Solution (A)>

First, a coating solution of the present invention will be described.

A coating solution (A) of the present invention contains a solvent, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, 0.01 to 0.35 chemical equivalent of an alkali metal compound relative to the amount of carboxyl group in the polycarboxylic acid-based polymer; and 0.05 to 0.75 chemical equivalent of a multivalent metal compound relative to the amount of the carboxyl group, wherein the number average molecular weight of the above polycarboxylic acid-based polymer is in the range of 40,000 to 10,000,000.

(First Solvent)

A first solvent related to the present invention is a medium for a polycarboxylic acid-based polymer described below and an alkali metal compound described below and a multivalent metal compound. Such first solvents include, for example, water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethylsulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate and butyl acetate. Of these, from the viewpoint of the environment, water, methyl alcohol, ethyl alcohol, and isopropyl alcohol are preferable. In addition, from the viewpoint of solubility of a polycarboxylic acid-based polymer and a multivalent metal compound, water is preferred. Additionally, these first solvents may be used alone or in a mixture of two or more species.

(Polycarboxylic Acid-Based Polymer)

A polycarboxylic acid-based polymer related to the present invention is produced by polymerization of a polycarboxylic acid-based polymerizable monomer and is a polymer having two or more carboxyl groups in its molecule. Such polycarboxylic acid-based polymers include, for example, (co)polymers of α,β-monoethylenically unsaturated carboxylic acids; copolymers of α,β-monoethylenically unsaturated carboxylic acids and other ethylenically unsaturated monomers; acidic polysaccharides such as alginic acid, carboxymethylcellulose, and the pectin that have carboxyl groups in their molecules. These polycarboxylic acid-based polymers may be used alone or in a mixture of two or more species.

In addition, such α,β-monoethylenically unsaturated carboxylic acids include, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and crotonic acid. Additionally, ethylenically unsaturated monomers that are copolymerizable with those α,β-monoethylenically unsaturated carboxylic acids include, for example, ethylene, propylene, vinyl carboxylates of saturated carboxylic acids such as vinyl acetate and the like, alkyl acrylates, alkyl methacrylates, alkyl itaconates, vinyl chloride, vinylidene chloride, styrene, acrylamides and acrylonitrile.

Among such polycarboxylic acid-based polymers, from the viewpoints of gas barrier properties of a resulting gas barrier film, gas barrier laminate and gas barrier multilayer film, a (co)polymer of at least one polymerizable monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid and a mixture thereof are preferably used. A (co)polymer of at least one polymerizable monomer selected from the group consisting of acrylic acid, methacrylic acid and maleic acid and a mixture thereof are more preferably used. Polyacrylic acid, polymethacrylic acid, polymaleic acid, and a mixture thereof are particularly preferably used.

Additionally, in a polycarboxylic acid-based polymer, from the viewpoints of gas barrier properties of a film and stability to a high-temperature water vapor and hot water, the oxygen permeation coefficient of a film molded only from a polycarboxylic acid-based polymer, which is to be a raw material, at a temperature of 30° C. and a relative humidity of 0% is preferably 1000 cm³ (STP)·μm/m²·day·MPa or less for use, more preferably 500 cm³ (STP)·μm/m²·day·MPa or less for use, particularly preferably 100 cm³ (STP)·μm/m²·day·MPa or less, most preferably 70 cm³ (STP)·μm/m²·day·MPa or less for use. Moreover, the oxygen permeation coefficient at a temperature of 30° C. and a relative humidity of 0% can be calculated by multiplying a measurement of a oxygen permeability coefficient at a temperature of 30° C. and a relative humidity of 0% [unit: cm³ (STP)/m²·day·MPa] by the thickness of a film (unit: μm).

In the coating solution (A) of the present invention, the number average molecular weight (Mn) measured by the GPC method of such a polycarboxylic acid-based polymer needs to be in the range of 40,000 to 10,000,000. If the number average molecular weight is less than 40,000, the resulting gas barrier film cannot have sufficient water resistance. In addition, it is not possible to obtain a packaging material which has gas barrier properties and transparency sufficiently prevented from deteriorating, and in which whitening is prevented. On the other hand, if the number average molecular weight exceeds 10,000,000, the viscosity of the coating solution is high, thereby losing coating suitability. Furthermore, from the viewpoint of water resistance of the resulting gas barrier film, the number average molecular weight of such a polycarboxylic acid-based polymer is preferably in the range of 70,000 to 5,000,000, more preferably in the range of 100,000 to 3,000,000, particularly preferably in the range of 150,000 to 2,000,000. In addition, polycarboxylic acid-based polymers with different number average molecular weights may be blended and used in predetermined amounts.

Moreover, in the coating solution (A) of the present invention, the content of such a polycarboxylic acid-based polymer needs to be in the range of 0.1 to 30 parts by weight relative to 100 parts by weight of the above solvent. If the content is less than 0.1 parts by weight, the resulting gas barrier film cannot have sufficient gas barrier properties. On the other hand, if the content exceeds 30 parts by weight, the coating solution is unstable, thereby being incapable of obtaining a uniform film. Furthermore, from the viewpoints of stability and the coating suitability of a coating solution, the content of such a polycarboxylic acid-based polymer is preferably in the range of 0.5 to 20 parts by weight, more preferably in the range of 1 to 10 parts by weight, relative to 100 parts by weight of the above solvent.

(Alkali Metal Compound)

Alkali metal compounds related to the present invention refer to alkali metals and alkali metal compounds. Such alkali metals include lithium, sodium, potassium, rubidium, cesium and francium. Meanwhile, such alkali metal compounds include oxides, hydroxides, carbonates, organic acid salts or inorganic acid salts of alkali metals. Additionally, such organic acid salts include, for example, formate salts, acetate salts, oxalate salts, citrate salts and lactate salts. Moreover, such inorganic acid salts include, for example, chlorides, sulfate salts, nitrate salts and phosphate salts.

Of these alkali metal compounds, from the viewpoints of gas barrier properties of resulting gas barrier films, gas barrier laminates and gas barrier multilayer films, sodium compounds and potassium compounds are preferably used, and hydroxides of sodium and potassium or carbonate salts thereof are preferably used.

Although the form of these alkali metal compounds may be particulate or non-particulate, the form is preferably particulate from the viewpoint of solubility. In addition, though the mean particle diameter of such particles is not particularly limited, it is preferably 1 cm or less, more preferably 7 mm or less, from the viewpoint of solubility.

Furthermore, in the coating solution (A) of the present invention, a content of such an alkali metal compound needs to be in the range of 0.01 to 0.35 chemical equivalent relative to the amount of carboxyl group in the above polycarboxylic acid-based polymer. If the content is less than 0.01 chemical equivalent, the coating solution is unstable, thereby a uniform film cannot be obtained. On the other hand, if the content exceeds 0.35 chemical equivalent, the resulting gas barrier film cannot have sufficient water resistance. In addition, it is not possible to obtain a packaging material which has gas barrier properties and transparency sufficiently prevented from deteriorating, and in which whitening is prevented. Moreover, from the viewpoints of stability of coating solutions (solubility of multivalent metal compounds described below) and gas barrier properties of resulting gas barrier films, the content of such an alkali metal compound is preferably in the range of 0.01 to 0.30 chemical equivalent, more preferably in the range of 0.01 to 0.20 chemical equivalent, relative to the amount of carboxyl group in the above polycarboxylic acid-based polymer. Furthermore, in the present invention, the use of combination of such an alkali metal compound and a multivalent metal compound described below can improve the water resistance of a resulting gas barrier film, sufficiently prevent the occurrence of whitening in the case of exposition of cold water also in a resulting packaging material, and also attain excellent gas barrier properties and transparency.

(Multivalent Metal Compound)

A multivalent metal compound related to the present invention refers to a simple substance of a multivalent metal atom, whose metal ion has a valence of two or more and refers to a compound thereof. Such multivalent metals include, for example, alkaline earth metals such as beryllium, magnesium and calcium; transition metals such as titanium, zirconium, chromium, manganese, iron, cobalt, nickel, copper and zinc; and aluminum. In addition, such multivalent metal compounds include, for example, oxides, hydroxides, carbonate salts, organic acid salts or inorganic acid salts, of the above multivalent metals; ammonium complexes or secondary to quaternary amine complexes or their carbonate salts or organic acid salts, of the above multivalent metals; or alkyl alkoxides of the above multivalent metals. Additionally, such organic acid salts include, for example, formate salts, acetate salts, oxalate salts, citrate salts and lactate salts. Moreover, such inorganic acid salts include, for example, chloride, sulfate salts, nitrate salts and phosphate salts.

Of these multivalent metal compounds, from the viewpoints of gas barrier properties, resistance to high-temperature water vapor and hot water and manufacturability, divalent metal compounds are preferably used. In addition, oxides, hydroxides, chlorides or carbonates of alkaline earth metals, cobalt, nickel, copper or zinc; and ammonium complexes of cobalt, nickel, copper or zinc or their carbonates are more preferably used. Moreover, oxides, hydroxides, chlorides or carbonate salts of magnesium, calcium, copper or zinc; and ammonium complexes of copper or zinc or their carbonates are particularly preferably used.

Although the form of these multivalent metal compounds may be particulate or non-particulate, the form is preferably particulate from the viewpoint of solubility. In addition, though the mean particle diameter of such a particle is not particularly limited, from the viewpoint of solubility, the mean particle diameter is preferably 50 μm or less, more preferably 30 μm or less particularly preferably 10 μm or less.

Furthermore, in the coating solution (A) of the present invention, the content of such a multivalent metal compound needs to be in the range of 0.05 to 0.75 chemical equivalent relative to the amount of carboxyl group in the above polycarboxylic acid-based polymer. If the content is less than 0.05 chemical equivalent, the resulting gas barrier film cannot have sufficient water resistance. In addition, it is not possible to obtain a packaging material which has gas barrier properties and transparency sufficiently prevented from deteriorating, and in which whitening is prevented. On the other hand, if the content exceeds 0.75 chemical equivalent, the coating solution is unstable, thereby being incapable of obtaining a uniform film. Furthermore, from the viewpoints of the stability of the coating solution and the water resistance of the resulting gas barrier film, the content of such a multivalent metal compound is preferably in the range of 0.05 to 0.60 chemical equivalent, more preferably in the range of 0.07 to 0.50 chemical equivalent, relative to the amount of carboxyl group in the above polycarboxylic acid-based polymer.

(Coating Solution (A))

In the coating solution (A) of the present invention, additives such as other polymers, softening agents, stabilizers, anti-blocking agents, adhesive agents, inorganic layered compounds, represented by montmorillonite and the like, can be added as appropriate, besides the solvent, the polycarboxylic acid-based polymer, the alkali metal compound and the multivalent metal compound, described above, within the range where the gas barrier properties of the resulting gas barrier film, gas barrier laminate and gas barrier multilayer film are not damaged. When such additives are used, the content of additive is preferably in the range of 0.1 to 100 parts by weight relative to 100 parts by weight of the above polycarboxylic acid-based polymer.

<Gas Barrier Film and Gas Barrier Laminate and Gas Barrier Multilayer Film>

Next, a gas barrier film, a gas barrier laminate, and a gas barrier multilayer film of the present invention will be described. A gas barrier film of the present invention comprises a layer (a) formed from the above-mentioned coating solution (A) and a support described below and has the layer (a) formed from the above coating solution (A) on at least one side of the above support. In addition, a gas barrier laminate of the present invention comprises the layer (a) formed from the above-mentioned coating solution (A), a layer (B) formed from a coating solution (B) described below and a support described below. The gas barrier laminate has, on at least one side of the support, at least one lamination unit in which the layer (a) formed from the coating solution (A) and the layer (b) formed from the coating solution (B) are paired so as to be mutually adjacent.

(Support)

A support related to the present invention is a support for sequentially laminating the layer (a) formed from the above-mentioned coating solution (A) and the layer (a) formed from the coating solution (B) described below. The form of such a support is not particularly limited, and the examples include the forms of a film, a sheet, and containers such as bottles, cups and trays.

In addition, the materials of such a support include, for example, metals, glasses, papers and plastics (including metal deposited plastics). Additionally, the materials of plastics of these materials include, for example, polyolefin-based polymers such as low density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene, poly(4-methyl pentene) and cyclic polyolefin and their copolymers and acid modified substances of the polymers and copolymers; vinyl acetate-based copolymers such as polyvinyl acetate, ethylene-vinyl acetate copolymers, saponified substances of ethylene-vinyl acetate copolymers and polyvinyl alcohol; polyester-based polymers such as polyethylene terephthalate, polybutylene terephthalate, poly(ε-caprolactone), polyhydroxybutyrate and polyhydroxyvalirate and their copolymers; polyamide-based polymers such as nylon 6, nylon 66, nylon 12, nylon 6, 66 copolymers, nylon 6, 12 copolymers and meta-xyleneadipamide-nylon 6 copolymers and their copolymers; polyether-based polymers such as polyethylene glycol, polyethersulfone, polyphenylene sulfides and polyphenylene oxides; chlorine-containing and fluorine-containing polymers such as polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride and polyvinylidene fluoride and their copolymers; acrylic-based polymers such as polymethyl acrylate, polyethyl acrylate, polymethyl methacrylate, polyethyl methacrylate and polyacrylonitrile and their copolymers; polyimide-based polymers and their copolymers; resins such as alkyd resin, melamine resin, acryl resin, nitrocellulose, urethane resin, unsaturated polyester resin, phenol resin, amino resin, fluoro resin and epoxy resin used for paints; and natural polymer compounds such as cellulose, starch, pullulan, chitin, chitosan, glucomannan, agarose and gelatin.

In addition, as for such supports, from the viewpoint of modifying the adhesion to the layer (a) formed from the above-mentioned coating solution (A) or the layer (b) formed from the coating solution (B) described below, a material in which the surface of a support may be activated by being subjected to corona treatment, flame treatment, plasma treatment and the like may be used, or a material in which an adhesive layer is disposed on the surface of a support may be used. A resin used for such an adhesive layer is not particularly limited so long as the resin is used for a dry laminate, an anchor coat and a primer, and the examples that can be used include alkyd resin, melamine resin, acryl resin, nitrocellulose, urethane resin, polyester resin, phenol resin, amino resin, fluoro resin and epoxy resin.

(Coating Solution (B))

The coating solution (B) related to the present invention contains the above multivalent metal compound and a second solvent. Such multivalent metal compounds include the ones as described above. In addition, in the coating solution (B) related to the present invention, the form of such a multivalent metal compound is preferably particulate. Additionally, the mean particle diameter of particles of such a multivalent metal compound may be a mean particle diameter similar to a multivalent metal compound used for the above-described coating solution (A). However, from the viewpoints of gas barrier properties and coating suitability, the mean particle diameter is preferably 5 μm or less, more preferably 1 μm or less, particularly preferably 0.1 μm or less.

The second solvent related to the present invention include, for example, water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, n-pentyl alcohol, dimethylsulfoxide, dimethylformamide, dimethylacetamide, toluene, hexane, heptane, cyclohexane, acetone, methyl ethyl ketone, diethyl ether, dioxane, tetrahydrofuran, ethyl acetate and butyl acetate. Of these, from the viewpoint of the coating properties, methyl alcohol, ethyl alcohol, isopropyl alcohol, toluene and ethyl acetate are preferable. In addition, from the viewpoint of manufacturability, methyl alcohol, ethyl alcohol, isopropyl alcohol and water are preferable. Additionally, a gas barrier film of the present invention is excellent in water resistance, and thus water can be used as the second solvent. Moreover, these second solvents may be used alone in a single species or in a mixture of two or more species.

In the coating solution (B) related to the present invention, additives such as a resin, a dispersing agent, a surfactant, a softening agent, a stabilizer, a membrane forming agent, an anti-blocking agent and a adhesive agents can be added as appropriate.

In this coating solution (B), a resin soluble or dispersible in a used solvent system is preferably mixed and used in order to improve coating suitability and film producing properties. The resins soluble or dispersible in the solvent system used in this manner include, for example, resins used for paints such as alkyd resins, melamine resins, acryl resins, nitrocellulose, urethane resins, polyester resins, phenol resins, amino resins, fluoro resins and epoxy resins.

Moreover, in this coating solution (B), a dispersing agent soluble or dispersible in a used solvent system is preferably mixed and used in order to improve the dispersibility of a multivalent metal compound. The dispersing agents soluble or dispersible in a solvent system used in this manner include, for example, substances such as acrylamide, acrylic acid, acrylic esters, neutralized acrylic acid, acrylonitrile, adipic acid, adipate ester, neutralized adipic acid, azelaic acid, abietic acid, aminododecanoic acid, arachidic acid, allylamine, arginine, arginine acid, alubumin, ammonia, itaconic acid, itaconate ester, neutralized itaconic acid, ethylene oxide, ethylene glycol, ethylenediamine, oleic acid, kaolin, casein, caprylic acid, caprolactam, xanthan gum, citric acid, glycine, cristobalite, glycerin, glycerin ester, glucose, crotonic acid, silicic acid, saccharose, salicylic acid, cycloheptene, oxalic acid, starch, stearic acid, sebacic acid, cellulose, ceresin, sorbitan oleate, sorbitan stearate, sorbitan palmitate, sorbitan behenate, sorbitan laurate, sorbitol, sorbic acid, talc, dextrine, terephthalic acid, dolomite, nitrocellulose, urea, vermiculite, palmitic acid, pinene, phthalic acid, fumaric acid, propionic acid, propylene glycol, hexamethylenediamine, pectin, behenic acid, benzyl alcohol, benzoin acid, benzoin acid ester, benzoguanamine, pentaerythritol, bentonite, boric acid, polydimethylsiloxane, polyvinyl alcohol, mica, maleic acid, maleate ester, neutralized maleic acid, malonic acid, mannitol, myristic acid, methacrylic acid, methylcellulose, palm oil, eugenol, butyric acid, lignocellulose, lysine, malic acid, phosphoric acid, lecithin, rosin and wax, or polymers or copolymers of these substances.

In addition, in the coating solution (B) related to the present invention, from the viewpoint of coating suitability, the percentage content of the multivalent metal compound and the additive of coating solution (B) in the coating solution (B) is preferably in the range of 1 to 50% by weight, more preferably in the range of 3 to 45% by weight, particularly preferably in the range of 5 to 40% by weight, relative to the total weight of the coating solution (B).

(Gas Barrier Film)

A gas barrier film of the present invention comprises the layer (a) formed from the above-mentioned coating solution (A) and the above-mentioned support, and has the layer (a) formed from the above coating solution (A) on at least one side of the above support.

In such a gas barrier film, from the viewpoints of gas barrier properties and productivity, the thickness of the layer (a) formed from the above coating solution (A) is preferably in the range of 0.01 to 10 μm, more preferably in the range of 0.05 to 5 μm, and particularly preferably in the range of 0.05 to 1 μm. In addition, in this gas barrier film, the oxygen permeability at a temperature of 30° C. and a relative humidity of 0% is preferably 1000 cm³ (STP)/m²·day·MPa or less, more preferably 500 cm³ (STP)/m²·day·MPa or less, particularly preferably 100 cm³ (STP)/m²·day·MPa or less, most preferably 70 cm³ (STP)/m²·day·MPa or less. Moreover, in the layer (a) formed from the coating solution (A) obtained by removal of the above support from such a gas barrier film, the oxygen permeability at a temperature of 30° C. and a relative humidity of 0% is preferably 1000 cm³ (STP)/m²·day·MPa or less, more preferably 500 cm³ (STP)/m²·day·MPa or less, particularly preferably 100 cm³ (STP)/m²·day·MPa or less, most preferably 70 cm³ (STP)/m²·day·MPa or less.

(Gas Barrier Laminate)

A gas barrier laminate of the present invention comprises the layer (a) formed from the above-mentioned coating solution (A) and the layer (B) formed from the coating solution (B) described above and the above-described support, the gas barrier laminate having, on at least one side of the support, at least one lamination unit in which the layer (a) formed from the coating solution (A) and the layer (b) formed from the coating solution (B) are adjacent to each other.

In such a gas barrier laminate, from the viewpoints of gas barrier properties and productivity, the thickness of the layer (a) formed from the above coating solution (A) is preferably in the range of 0.01 to 10 μm, more preferably in the range of 0.05 to 5 μm, particularly preferably in the range of 0.05 to 1 μm. In addition, in such a gas barrier laminate, from the viewpoints of gas barrier properties and productivity, the thickness of the layer (b) formed from the above coating solution (B) is preferably in the range of 0.01 to 10 μm, more preferably in the range of 0.05 to 5 μm, particularly preferably in the range of 0.05 to 1 μm. Additionally, the laminate aspects of the layer (a) formed from the above coating solution (A) and the layer (b) formed from the above coating solution (B) of the present invention include an aspect of, for example, (a)/(b), (b)/(a), (a)/(b)/(a) and (b)/(a)/(b) laminated in the order from one side of the above support.

In addition, in this gas barrier laminate, the oxygen permeability at a temperature of 30° C. and a relative humidity of 0% is preferably 1000 cm³ (STP)/m²·day·MPa or less, more preferably 500 cm³ (STP)/m²·day·MPa or less, particularly preferably 100 cm³ (STP)/m²·day·MPa or less, most preferably 70 cm³ (STP)/m²·day·MPa or less.

In addition, a material comprising such a gas barrier laminate can be suitably used as a packaging material for foods, beverages, chemicals, medicines and precision metal components such as electronic components that are subject to deterioration by influence of oxygen or the like, as a packaging material for articles that need processing (heat sterilization) such as boiling and retort sterilization, under high-temperature hot water conditions or their packages. Additionally, for example, in the case where a packaging material is used for a heat sterilization packaging application or the like, even if a packaging material is exposed to cold water of 30° C. or less, in such a packaging material, whitening can be sufficiently prevented, and also which is excellent in gas barrier properties and transparency. Thus such a packaging material can be suitably used particularly as a packaging material for a heat sterilization packaging application.

(Gas Barrier Multilayer Film)

The gas barrier multilayer film of the present invention comprises the above-described gas barrier laminate and a plastic film laminated on at least one side of the above gas barrier laminate.

Such a plastic film can be selected as appropriate depending on the object of strength impartment, seal performance impartment and open-easiness impartment during sealing, design impartment, light shielding impartment, moisture resistance impartment, or the like, and is not particularly limited. The examples can include films of materials similar to the materials of plastics in the above-described support. In addition, such plastic films may be used alone in a single species or in a laminate of two or more species. Additionally, the thickness of this plastic film is preferably from 1 to 1000 μm, more preferably from 5 to 500 μm, particularly preferably from 5 to 200 μm, most preferably from 5 to 150 μm.

In such a gas barrier multilayer film, the oxygen permeability at a temperature of 30° C. and a relative humidity of 0% is preferably 1000 cm³ (STP)/m²·day·MPa or less, more preferably 500 cm³ (STP)/m²·day·MPa or less, particularly preferably 100 cm³ (STP)/m²·day·MPa or less, most preferably 70 cm³ (STP)/m²·day·MPa or less.

Additionally, in such a gas barrier multilayer film, from the viewpoint of the storability of contents, the oxygen permeability at a temperature of 30° C. and under a high moisture condition of a relative humidity of 80% is preferably 100 cm³ (STP)/m²·day·MPa or less, more preferably 70 cm³ (STP)/m²·day·MPa or less, particularly preferably 50 cm³ (STP)/m²·day·MPa or less.

Though the laminate aspect of a plastic film in such a gas barrier multilayer film is not particularly limited, from the viewpoint of handling as a product, preferred laminate aspects include polyethylene terephthalate/layer (a)/layer (b)/polyolefin, nylon/layer (a)/layer (b)/polyolefin, polypropylene/layer (a)/layer (b)/polyolefin, paper/layer (a)/layer (b)/polyolefin, polyethylene terephthalate/layer (a)/layer (b)/layer (a)/polyolefin, polyethylene terephthalate/layer (a)/layer (b)/nylon/polyolefin and polyethylene terephthalate/layer (a)/layer (b)/metal deposited nylon/polyolefin. Of these, polyethylene terephthalate/layer (a)/layer (b)/polyolefin, polyethylene terephthalate/layer (a)/layer (b)/nylon/polyolefin, polyethylene terephthalate/layer (a)/layer (b)/metal deposited nylon/polyolefin are more preferred and polyethylene terephthalate/layer (a)/layer (b)/polyolefin and polyethylene terephthalate/layer (a)/layer (b)/nylon/polyolefin are particularly preferred.

<Manufacturing Method of Gas Barrier Film, Gas Barrier Laminate and Gas Barrier Multilayer Film>

Next, methods of manufacturing a gas barrier film, a gas barrier laminate, and a gas barrier multilayer film of the present invention will be described.

(Method of Manufacturing Gas Barrier Film)

The method of manufacturing a gas barrier film of the present invention is a method of applying the above-described coating solution (A) to at least one side of the above-described support and then drying the solution to obtain a gas barrier film having the layer (a) formed from the above coating solution (A).

The method of applying the above coating solution (A) is not particularly limited and the examples include a method of application by means of a reverse roll coating machine such as an air knife coater, a direct gravure coater, a gravure offset, an arc gravure coater, a top feeding reverse coater, a bottom feeding reverse coater, or a nozzle feeding reverse coater; or a five roll coater, a lip coater, a barcoater, bar reverse coater or a die coater.

In addition, the method of drying the above coating solution (A) is not particularly limited, and the methods can include a method by natural drying, a method of drying in an oven set to a predetermined temperature, and a method using a dryer with a coater, for example, an arch drier, a floating dryer, a drum drier, an infrared ray drier, or the like. Additionally, the drying conditions can be selected as appropriate depending on a method of drying. For example, in a method of drying in an oven, the drying temperature is preferably from 40 to 350° C., more preferably from 40 to 325° C., particularly preferably from 50 to 300° C. Moreover, the drying time is preferably from 0.5 sec to 10 min, more preferably from 1 sec to 5 min, particularly preferably from 1 sec to 1 min.

(Method of Manufacturing Gas Barrier Laminate)

A method of manufacturing a gas barrier laminate of the present invention is a method that entails applying the above-described coating solution (A) and the above described coating solution (B) to at least one side of the above-described support and drying the resulting material to thereby obtain a gas barrier laminate having, on at least one side of the support, at least one lamination unit in which the layer (a) formed from the coating solution (A) and the layer (b) formed from the coating solution (B) are adjacent to each other.

The method of applying the above coating solution (A) and the method of drying the above coating solution (A) can include the methods as described above. In addition the methods of applying and drying the above coating solution (B) can include the vapor phase coating processes such as a vapor-deposition method, a sputtering method, and an ion plating method, in addition to methods similar to the methods of applying and drying the above-described coating solution (A) in the above-described method of manufacturing a gas barrier film.

Furthermore, the order of applying the above coating solution (A) and the above coating solution (B) may be an order in which the above coating solution (A) is applied to at least one side of the above support and dried, and then the above coating solution (B) is applied and dried or may be an order in which the above coating solution (B) is applied to at least one side of the above support and dried, and then the above coating solution (A) is applied and dried.

(Method of Manufacturing Gas Barrier Multilayer Film)

The method of manufacturing a gas barrier multilayer film of the present invention is a method of laminating a plastic film to at least one side of a gas barrier laminate as described above to thereby obtain the above-described gas barrier multilayer film.

A method of laminating a plastic film in such a way can be selected as appropriate from well-known laminating methods and is not particularly limited. The examples include a dry laminating method, a wet laminating method and an extruding laminating method.

EXAMPLE

The present invention will be described more specifically on the basis of Examples and Comparative Examples hereinafter; however, the invention is by no means limited to the Examples below. In addition, the oxygen permeability coefficient of a polycarboxylic acid-based polymer used as a raw material was measured by the following method.

<Measurement of Oxygen Permeability Coefficient of Polycarboxylic Acid-Based Polymer Used as Raw Material>

A solution of 5 parts by weight of polyacrylic acid (polycarboxylic acid-based polymer) diluted with 100 parts by weight of water was applied to a corona-treated side of a biaxially oriented polyester film (support) having a thickness of 12 μm using a mayer bar and then the resulting material was dried at 90° C. for 30 seconds. The material as a film sample was measured to obtain an oxygen permeability coefficient. In other words, the oxygen permeability of the film sample was measured using an oxygen permeation tester (OX-TRAN2/20: available from MOCON Inc.) at a temperature of 30° C. and a relative humidity (RH) of 0% on the both sides. Then, the measurement of the resulting oxygen permeability (unit: cm³ (STP)/m²·day·MPa) was multiplied by the thickness of a polyacrylic acid layer (unit: μm) to calculate the oxygen permeability coefficient (unit: cm³ (STP)·μm/m²·day·MPa).

<Coating Solution>

(i) Preparation of Coating Solutions

Example 1

5 Parts by weight of polyacrylic acid (available from Toagosei Co., Ltd., Aron A-10H, Mn: 200,000, oxygen permeability coefficient 50 cm³ (STP)·μm/m²·day·MPa) was diluted with 100 parts by weight of water. Thereafter, relative to the amount of carboxyl group of polyacrylic acid, 0.10 chemical equivalent of sodium hydroxide (particulate, particle diameter: 5 μm) as an alkali metal compound and 0.30 chemical equivalent of zinc oxide (particulate, particle diameter: 5 μm) as a multivalent metal compound were added thereto and then the resulting material was agitated at room temperature for two days to prepare a coating solution (A).

Example 2

A coating solution (A) was prepared similarly to Example 1 except that polyacrylic acid (available from Polysciences Inc., Mn: 50,000, oxygen permeability coefficient: 50 cm³ (STP)·μm/m²·day·MPa) was used in place of the polyacrylic acid (Aron A-10H).

Example 3

A coating solution (A) was prepared similarly to Example 1 except that 0.05 chemical equivalent of sodium hydroxide was used as the alkali metal compound and 0.10 chemical equivalent of calcium chloride (particulate, particle diameter: 5 μm) was used as the multivalent metal compound.

Example 4

A coating solution (A) was prepared similarly to Example 1 except that 0.40 chemical equivalent of calcium hydroxide was used as the multivalent metal.

Example 5

A coating solution (A) was prepared similarly to Example 1 except that 0.30 chemical equivalent of sodium hydroxide was used as the alkali metal compound and 0.70 chemical equivalent of calcium hydroxide (particulate, particle diameter: 8 μm) was used as the multivalent metal compound.

Comparative Example 1

A coating solution (A) for comparison was prepared similarly to Example 1 except that 0.30 chemical equivalent of sodium hydroxide was used as the alkali metal compound and 0.80 chemical equivalent of calcium hydroxide was used as the multivalent metal compound.

Comparative Example 2

A coating solution (A) for comparison was prepared similarly to Example 4 except that the alkali metal compound was not added.

(ii) Evaluation of Coating Solution

The appearance of each resultant coating solution was visually observed. Then, the case where a multivalent metal was dissolved in the coating solution and the appearance was transparent was determined to be “passed.” The case where part of a multivalent metal was not dissolved and the multivalent metal deposited was determined to be “failed.” The results obtained and the compositions of the coating solutions used in Examples and Comparative Examples are listed in Table 1.

TABLE 1 Composition of coating solution (A) Number average Coating molecular Parts by weight solution (A) weight of of Alkaline Chemical Multivalent Chemical Appearance of Carboxylic polycarboxylic polycarboxylic metal equivalent metal equivalent coating acids acid acid (*1) compound (*2) compound (*2) solution Example 1 Polyacrylic 200,000 5 Sodium 0.10 Zinc oxide 0.30 Passed acid hydroxide Example 2 Polyacrylic 50,000 5 Sodium 0.10 Zinc oxide 0.30 Passed acid hydroxide Example 3 Polyacrylic 200,000 5 Sodium 0.05 Calcium 0.10 Passed acid hydroxide chloride Example 4 Polyacrylic 200,000 5 Sodium 0.10 Calcium 0.40 Passed acid hydroxide hydroxide Example 5 Polyacrylic 200,000 5 Sodium 0.30 Calcium 0.70 Passed acid hydroxide hydroxide Comparative Polyacrylic 200,000 5 Sodium 0.30 Calcium 0.80 Failed Example 1 acid hydroxide hydroxide Comparative Polyacrylic 200,000 5 — — Calcium 0.40 Failed Example 2 acid hydroxide (*1) The parts by weight indicates a parts by weight of polycarboxylic acid relative to 100 weight parts of water. (*2) The chemical equivalent indicates a chemical equivalent of a metal compound relative to the carboxyl group of polycarboxylic acid.

<Gas Barrier Film>

(i) Fabrication of Gas Barrier Film

Example 6

The coating solution (A) obtained in Example 1 was applied to the corona-treated side of a biaxially oriented polyester film (support) having a thickness of 12 μm using a mayer bar and the resulting material was dried at 90° C. for 30 seconds to obtain a gas barrier film comprising the layer (a) having a thickness of 0.3 μm formed from the coating solution (A).

Examples 7 to 10

Each gas barrier film was obtained similarly to Example 6 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) obtained in Example 2 (Example 7), the coating solution (A) obtained in Example 3 (Example 8), the coating solution (A) obtained in Example 4 (Example 9), or the coating solution (A) obtained in Example 5 (Example 10) was used.

Comparative Example 3

First, 5 parts by weight of polyacrylic acid (available from Toagosei Co., Ltd., Aron A-10H, Mn: 200,000, oxygen permeability coefficient: 50 cm³ (STP)·μm/m²·day·MPa) was diluted with 100 parts by weight of water to prepare a coating solution for comparison. Then, a gas barrier film for comparison was obtained similarly to Example 6 except that the resulting coating solution (A) for comparison was used in place of the coating solution (A) obtained in Example 1.

Comparative Example 4

First, 5 parts by weight of polyacrylic acid (available from Toagosei Co., Ltd., Aron A-10H, Mn: 200,000, oxygen permeability coefficient: 50 cm³ (STP)·μm/m²·day·MPa) was diluted with 100 parts by weight of water. Thereafter, 0.03 chemical equivalent of sodium hydroxide relative to the amount of carboxyl group of polyacrylic acid was added thereto and the resultant material was agitated at room temperature for two days to prepare a coating solution (A) for comparison. Then, a gas barrier film for comparison was obtained similarly to Example 6 except that the resulting coating solution (A) for comparison was used in place of the coating solution (A) obtained in Example 1.

Comparative Example 5

First, 5 parts by weight of polyacrylic acid (available from Toagosei Co., Ltd., Aron A-10H, Mn: 200,000, oxygen permeability coefficient: 50 cm³ (STP)·μm/m²·day·MPa) was diluted with 100 parts by weight of water. Thereafter, 0.03 chemical equivalent of zinc oxide relative to the amount of carboxyl group of polyacrylic acid was added thereto and the resultant material was agitated at room temperature for two days to prepare a coating solution (A) for comparison. Then, a gas barrier film for comparison was obtained similarly to Example 6 except that the resulting coating solution (A) for comparison was used in place of the coating solution (A) obtained in Example 1.

Comparative Example 6

First, 5 parts by weight of polyacrylic acid (available from Toagosei Co., Ltd., Aron A-10H, Mn: 200,000, oxygen permeability coefficient: 50 cm³ (STP)·μm/m²·day·MPa) was diluted with 100 parts by weight of water. Thereafter, 0.03 chemical equivalent of calcium hydroxide relative to the amount of carboxyl group of polyacrylic acid was added thereto and the resultant material was agitated at room temperature for two days to prepare a coating solution (A) for comparison. Then, a gas barrier film for comparison was obtained similarly to Example 6 except that the resulting coating solution (A) for comparison was used in place of the coating solution (A) obtained in Example 1.

Comparative Example 7

First, 5 parts by weight of polyacrylic acid (available from Nihon Jyunyaku Co., Ltd., Jurymer AC-10L, Mn: 25,000, oxygen permeability coefficient: 50 cm³ (STP)·μm/m²·day·MPa) was diluted with 100 parts by weight of water. Thereafter, relative to the amount of carboxyl group of polyacrylic acid, 0.05 chemical equivalent of sodium hydroxide as the alkali metal compound and 0.15 chemical equivalent of zinc oxide as the multivalent metal compound were added thereto and the resultant material was agitated at room temperature for two days to prepare a coating solution (A) for comparison. Then, a gas barrier film for comparison was obtained similarly to Example 6 except that the resulting coating solution (A) for comparison was used in place of the coating solution (A) obtained in Example 1.

(ii) Evaluation of Water Resistance of Gas Barrier Film

Each resultant gas barrier film was immersed in cold water at a temperature of 20° C. for one second. The material taken out was taken as a film sample and subjected to oxygen permeability measurement. The water resistance of the gas barrier film was evaluated on the basis of the measurement. In other words, the oxygen permeability of the film sample was measured using an oxygen permeation tester (OX-TRAN2/20: available from MOCON Inc.) at a temperature of 30° C. and a relative humidity (RH) of 0% on the both sides. Then, the case where the measurement of the resulting oxygen permeability was less than 50 cm³ (STP)/m²·day·MPa was determined to be “passed.” The case where the measurement of the resulting oxygen permeability was 50 cm³ (STP)/m²·day·MPa or larger was determined to be “failed.” The results obtained and the compositions of the coating solutions used in the Examples and Comparative Examples are listed in Table 2. In addition, the measurement result of the oxygen permeability of the biaxially oriented polyester film having a thickness of 12 μm is shown in Table 2 as Reference Example 1.

TABLE 2 Gas barrier film Oxygen perme- ability after Composition of coating solution (A) immersion in Number average Parts by cold water at molecular weight of a temperature weight of polycar- Alkali Chemical Multivalent Chemical of 30° C. and 0% Carboxylic polycarboxylic boxylic metal equivalent metal equivalent RH (cm³ (STP)/ water acids acid acid (*3) compound (*4) compound (*4) m² · day · MPa) resistance Example 6 Polyacrylic 200,000 5 Sodium 0.10 Zinc oxide 0.30 24 Passed acid hydroxide Example 7 Polyacrylic 50,000 5 Sodium 0.10 Zinc oxide 0.30 26 Passed acid hydroxide Example 8 Polyacrylic 200,000 5 Sodium 0.05 Calcium 0.10 32 Passed acid hydroxide chloride Example 9 Polyacrylic 200,000 5 Sodium 0.10 Calcium 0.40 21 Passed acid hydroxide hydroxide Example 10 Polyacrylic 200,000 5 Sodium 0.30 Calcium 0.70 48 Passed acid hydroxide hydroxide Comparative Polyacrylic 200,000 5 — — — — 1800 Failed Example 3 acid Comparative Polyacrylic 200,000 5 Sodium 0.03 — — 1880 Failed Example 4 acid hydroxide Comparative Polyacrylic 200,000 5 — — Zinc oxide 0.03 1750 Failed Example 5 acid Comparative Polyacrylic 200,000 5 — — Calcium 0.03 1610 Failed Example 6 acid hydroxide Comparative Polyacrylic 25,000 5 Sodium 0.05 Zinc oxide 0.15 450 Failed Example 7 acid hydroxide Reference — — — — — — — 2000 — Example 1 (*3) The parts by weight indicates a parts by weight of polycarboxylic acid relative to 100 parts by weight of water. (*4) The chemical equivalent indicates a chemical equivalent of a metal compound relative to the carboxyl group of polycarboxylic acid.

As apparent from the results listed in Table 2, it is verified that the gas barrier film of the present invention has excellent water resistance.

<Gas Barrier Laminate>

(i) Fabrication of gas barrier laminate

Example 11

First, the coating solution (A) obtained in Example 1 was applied to the corona-treated side of a biaxially oriented polyester film (support) having a thickness of 12 μm using a mayer bar and the resulting material was dried at a temperature of 90° C. for 30 seconds to obtain the layer (a) having a thickness of 0.3 μm formed from the coating solution (A). Next, the coating solution (B) produced by dispersing 10 parts by weight of zinc oxide particulates having an average particle diameter of 20 m into 100 parts by weight of water was applied to the surface of the above-described layer (a) using a mayer bar and the resulting material was dried at a temperature of a temperature of 90° C. for 30 seconds to form the layer (b) having a thickness of 0.5 μm formed from the coating solution (B), thereby fabricating a gas barrier laminate.

Examples 12 to 14

Each gas barrier laminate was fabricated similarly to Example 11 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) obtained in Example 2 (Example 12), the coating solution (A) obtained in Example 3 (Example 13), or the coating solution (A) obtained in Example 4 (Example 14) was used.

Comparative Examples 8 to 12

Each gas barrier laminate for comparison was obtained similarly to Example 11 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) used in Comparative Example 3 (Example 8), the coating solution (A) used in Comparative Example 4 (Comparative Example 9), the coating solution (A) used in Comparative Example 5 (Comparative Example 10), the coating solution (A) used in Comparative Example 6 (Comparative Example 11), or the coating solution (A) used in Comparative Example 7 (Comparative Example 12) was used.

(ii) Measurement of Oxygen Permeability and Evaluation of Water Resistance

Each resultant gas barrier laminate was taken as a film sample and subjected to oxygen permeability measurement. In other words, the oxygen permeability of a film sample was measured at a temperature of 30° C. and a relative humidity of 0% (RH) on both sides using an oxygen permeation tester (OX-TRAN2/20; available from MOCON Inc.). The units are cm³ (STP)/m²·day·MPa. In addition, the appearance of a film sample was visually observed, and water resistance of a gas barrier laminate was evaluated. The case where a film sample had no whitening and no deteriorating of transparency was determined to be “passed.” The case where a film sample had whitening or deteriorating of transparency due to the breakage of the film was determined to be “failed.” The results obtained and the compositions of the coating solutions used in the Examples and Comparative Examples are listed in Table 3.

TABLE 3 Gas barrier laminate Composition of coating solution (A) (*5) Oxygen Number permeability average Composition of at a molecular coating solution (B) temperature of weight of Alkali Chemical Multivalent Chemical Multivalent 30° C. and 0% polyacrylic metal equivalent metal equivalent metal RH (cm³ (STP)/ Water acid compound (*6) compound (*6) compound Solvent m² · day · MPa) resistance Example 11 200,000 Sodium 0.10 Zinc oxide 0.30 Zinc oxide Water 24 Passed hydroxide Example 12 50,000 Sodium 0.10 Zinc oxide 0.30 Zinc oxide Water 26 Passed hydroxide Example 13 200,000 Sodium 0.05 Calcium 0.10 Zinc oxide Water 32 Passed hydroxide chloride Example 14 200,000 Sodium 0.10 Calcium 0.40 Zinc oxide Water 21 Passed hydroxide hydroxide Comparative 200,000 — — — — Zinc oxide Water 1800 Failed Example 8 Comparative 200,000 Sodium 0.03 — — Zinc oxide Water 1880 Failed Example 9 hydroxide Comparative 200,000 — — Zinc oxide 0.03 Zinc oxide Water 1750 Failed Example 10 Comparative 200,000 — — Calcium 0.03 Zinc oxide Water 1610 Failed Example 11 hydroxide Comparative 25,000 Sodium 0.05 Zinc oxide 0.15 Zinc oxide Water 450 Failed Example 12 hydroxide (*5) The amount of polyacrylic acid in the coating solution (A) is 5 parts by weight relative to 100 parts by weight of water. (*6) The chemical equivalent indicates a chemical equivalent of a metal compound relative to the carboxyl group of polyacrylic acid.

As apparent from the results listed in Table 3, it is verified that, in the present invention, a gas barrier laminate having excellent oxygen barrier properties and transparency is obtained even when water is used as a solvent for the coating solution (B).

(iii) Fabrication of Gas Barrier Laminate for Water Resistance Evaluation

Example 15

First, the coating solution (A) obtained in Example 1 was applied to the corona-treated side of a biaxially oriented polyester film (support) having a thickness of 12 μm using a mayer bar and the resulting material was dried at a temperature of 90° C. for 30 seconds to form the layer (a) having a thickness of 0.3 μm formed from the coating solution (A). Next, a zinc oxide particulate toluene dispersion liquid (available from Sumitomo Osaka Cement Co., Ltd., zinc oxide dispersion paint ZR133, solid concentration: 33% by weight) was applied to the surface of the above-described layer (a) using a mayer bar and the resulting material was dried at a temperature of 90° C. for 30 seconds to form the layer (b) having a thickness of 0.5 μm formed from the coating solution (B), thereby fabricating a gas barrier laminate.

Examples 16 to 18

Each gas barrier laminate was fabricated similarly to Example 15 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) obtained in Example 2 (Example 16), the coating solution (A) obtained in Example 3 (Example 17), or the coating solution (A) obtained in Example 4 (Example 18) was used.

Comparative Example 13 to 17

Each gas barrier laminate for comparison was fabricated similarly to Example 15 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) used in Comparative Example 3 (Example 13), the coating solution (A) used in Comparative Example 4 (Comparative Example 14), the coating solution (A) used in Comparative Example 5 (Comparative Example 15) the coating solution (A) used in Comparative Example 6 (Comparative Example 16), or the coating solution (A) used in Comparative Example 7 (Comparative Example 17) was used.

(iv) Evaluation of Water Resistance of Gas Barrier Laminate

Each resultant gas barrier laminate was immersed in cold water at a temperature of 20° C. for three minutes and then used as a film sample. The film sample was subjected to evaluation or measurement of water resistance and oxygen permeability after immersion in cold water. In other words, the appearance of the film sample after immersed in cold water was visually observed, and the water resistance of the gas barrier laminate was evaluated. The case where a film sample exhibited no whitening and no deteriorating of transparency was determined to be “good” and the case where a film sample exhibited whitening was determined to be “whitened.” In addition, the oxygen permeability of a film sample after immersed in cold water was measured by the same method as the above. The results obtained and the compositions of the coating solutions used in Examples and Comparative Examples are listed in Table 4.

TABLE 4 Gas barrier laminate Composition of coating solution (A) (*7) Oxygen Number permeability at a average Composition of temperature of molecular coating solution (B) 30° C. and 0% RH weight of Alkali Chemical Multivalent Chemical Multivalent after immersion polyacrylic metal equivalent metal equivalent metal Water in cold water acid compound (*8) compound (*8) compound Solvent resistance (cm³ (STP)/m² · day · MPa) Example 15 200,000 Sodium 0.10 Zinc oxide 0.30 Zinc oxide Toluene Good 35 hydroxide Example 16 50,000 Sodium 0.10 Zinc oxide 0.30 Zinc oxide Toluene Good 37 hydroxide Example 17 200,000 Sodium 0.05 Calcium 0.10 Zinc oxide Toluene Good 41 hydroxide chloride Example 18 200,000 Sodium 0.10 Calcium 0.40 Zinc oxide Toluene Good 31 hydroxide hydroxide Comparative 200,000 — — — — Zinc oxide Toluene Whitened 570 Example 13 Comparative 200,000 Sodium 0.03 — — Zinc oxide Toluene Whitened 580 Example 14 hydroxide Comparative 200,000 — — Zinc oxide 0.03 Zinc oxide Toluene Whitened 520 Example 15 Comparative 200,000 — — Calcium 0.03 Zinc oxide Toluene Whitened 520 Example 16 hydroxide Comparative 25,000 Sodium 0.05 Zinc oxide 0.15 Zinc oxide Toluene Whitened 170 Example 17 hydroxide (*7) The amount of polyacrylic acid in the coating solution (A) is 5 parts by weight relative to 100 parts by weight of water. (*8) The chemical equivalent indicates a chemical equivalent of a metal compound relative to the carboxyl group of polyacrylic acid.

As apparent from the results listed in Table 4, it is verified that the gas barrier laminate of the present invention has excellent water resistance and excellent oxygen barrier properties even when exposed to cold water. Hence, according to the present invention, it is verified that even when the packaging material is exposed to cold water of 30° C. or less, the occurrence of whitening can be sufficiently prevented and also a packaging material that is excellent in gas barrier properties and transparency can be obtained.

<Gas Barrier Multilayer Film>

(i) Fabrication of Gas Barrier Multilayer Film

Example 19

First, the coating solution (A) obtained in Example 1 was applied to the corona-treated side of a biaxially oriented polyester film (support) having a thickness of 12 μm using a mayer bar and the resulting material was dried at a temperature of 90° C. for 30 seconds to form the layer (a) having thickness of 0.3 μm formed from the coating solution (A). Next, the coating solution (B) produced by dispersing 10 parts by weight of zinc oxide particulates having an average particle diameter of 20 nm into 100 parts by weight of water was applied to the surface of the above-described layer (a) using a mayer bar and the resulting material was dried at a temperature of 90° C. for 30 seconds to form the layer (b) having a thickness of 0.5 μm formed from the coating solution (B), thereby fabricating a gas barrier laminate. Then, a urethane-based adhesive was applied to the surface of the above-mentioned layer (b) and then a polypropylene film having a thickness of 60 μm was laminated thereon to fabricate a gas barrier multilayer film.

Example 20

First, a urethane-based adhesive (available from MITSUI TAKEDA CHEMICALS, INC., Takelac A-620, hardener: Takenate A-65) was applied to the corona-treated side of a biaxially oriented polyester film (support) having a thickness of 12 μm using a mayer bar so as to make the thickness 0.1 μm and the resulting material was dried at a temperature of 90° C. for 30 seconds to form an anchor coat layer. Then, a gas barrier multilayer film was fabricated similarly to Example 19 except that the coating solution (A) was applied to the surface of the above-described anchor coat layer.

Examples 21 and 22

Each gas barrier multilayer film was fabricated similarly to Example 19 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) obtained in Example 2 (Example 21), or the coating solution (A) obtained in Example 3 (Example 22) was used.

Example 23

A gas barrier multilayer film was fabricated similarly to Example 19 except that a biaxially oriented polyamide film having a thickness of 15 μm was used in place of the biaxially oriented polyester film having a thickness of 12 μm.

Example 24

First, a urethane-based adhesive (available from MITSUI TAKEDA CHEMICALS, INC., Takelac A-620, hardener:

Takenate A-65) was applied to the corona-treated side of a biaxially oriented polypropylene film (support) having a thickness of 20 μm using a mayer bar so as to make the thickness 0.1 μm and the resulting material was dried at a temperature of 90° C. for 30 seconds to form an anchor coat layer. Then, a gas barrier multilayer film was fabricated similarly to Example 19 except that the coating solution (A) was applied to the surface of the above-described anchor coat layer.

Example 25

A gas barrier multilayer film was fabricated similarly to Example 19 except that the coating solution (A) obtained in Example 4 was used in place of the coating solution (A) obtained in Example 1.

Comparative Examples 18 to 22

Each gas barrier multilayer film for comparison was fabricated similarly to Example 19 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) used in Comparative Example 3 (Comparative Example 18), the coating solution (A) used in Comparative Example 4 (Comparative Example 19), the coating solution (A) used in Comparative Example 5 (Comparative Example 20), the coating solution (A) used in Comparative Example 6 (Comparative Example 21), or the coating solution (A) used in Comparative Example 7 (Comparative Example 22) was used.

(ii) Measurement of Oxygen Permeability

Each resultant gas barrier multilayer film was taken as a film sample and subjected to oxygen permeability measurement. In other words, the oxygen permeability of a film sample was measured at a temperature of 30° C. and a relative humidity of 0% (RH) on both sides using an oxygen permeation tester (OX-TRAN2/20; available from MOCON Inc.). In addition, the units are cm³ (STP)/m²·day·MPa. Additionally, the appearance of a film sample was visually observed, and water resistance of a gas barrier multilayer film was evaluated. The case where a film sample had no whitening and no deteriorating of transparency was determined to be “passed.” The case where a film sample had whitening or deteriorating of transparency due to the breakage of the film was determined to be “failed.” The results obtained and the compositions of the supports and the coating solution (A) used in the Examples and Comparative Examples are listed in Table 5.

TABLE 5 Gas barrier multilayer film Oxygen Composition of coating solution (A) (*9) permeability Number at a average temperature Composition of support molecular of 30° C. Anchor weight of Alkali Chemical Multivalent Chemical and 0% coat polyacrylic metal equivalent metal equivalent RH (cm³ (STP)/ Water Material layer acid compound (*10) compound (*10) m² · day · MPa) resistance Example 19 Biaxially oriented None 200,000 Sodium 0.10 Zinc oxide 0.30 9 Passed polyester hydroxide Example 20 Biaxially oriented Present 200,000 Sodium 0.10 Zinc oxide 0.30 8 Passed polyester hydroxide Example 21 Biaxially oriented None 50,000 Sodium 0.10 Zinc oxide 0.30 12 Passed polyester hydroxide Example 22 Biaxially oriented None 200,000 Sodium 0.05 Calcium 0.10 15 Passed polyester hydroxide chloride Example 23 Biaxially oriented None 200,000 Sodium 0.10 Zinc oxide 0.30 17 Passed polyamide hydroxide Example 24 Biaxially oriented Present 200,000 Sodium 0.10 Zinc oxide 0.30 25 Passed polypropylene hydroxide Example 25 Biaxially oriented None 200,000 Sodium 0.10 Calcium 0.40 18 Passed polyester hydroxide hydroxide Comparative Biaxially oriented None 200,000 — — — — 1280 Failed Example 18 polyester Comparative Biaxially oriented None 200,000 Sodium 0.03 — — 1290 Failed Example 19 polyester hydroxide Comparative Biaxially oriented None 200,000 — — Zinc oxide 0.03 1210 Failed Example 20 polyester Comparative Biaxially oriented None 200,000 — — Calcium 0.03 1110 Failed Example 21 polyester hydroxide Comparative Biaxially oriented None 25,000 Sodium 0.05 Zinc oxide 0.15 750 Failed Example 22 polyester hydroxide (*9) The amount of polyacrylic acid in the coating solution (A) is 5 parts by weight relative to 100 parts by weight of water. (*10) The chemical equivalent indicates the chemical equivalent of a metal compound relative to the carboxyl group of polyacrylic acid.

As apparent from the results listed in Table 5, it is verified that, in the present invention, a gas barrier multilayer film that exhibits excellent oxygen barrier properties is obtained even when water is used as a solvent for the coating solution (B).

(iii) Fabrication of Gas Barrier Multilayer Film

Example 26

First, the coating solution (A) obtained in Example 1 was applied to the corona-treated side of a biaxially oriented polyester film (support) having a thickness of 12 rpm using a mayer bar and the resulting material was dried at a temperature of 90° C. for 30 seconds to form the layer (a) having a thickness of 0.3 μm formed from the coating solution (A). Next, a zinc oxide particulate toluene dispersion liquid (available from Sumitomo Osaka Cement Co., Ltd., zinc oxide dispersion paint ZR133, solid concentration: 33% by weight) was applied to the surface of the above-described layer (a) using a mayer bar and the resulting material was dried at a temperature of 90° C. for 30 seconds to form the layer (b) having a thickness of 0.5 μm formed from the coating solution (B), thereby fabricating a gas barrier laminate. Then, a urethane-based adhesive was applied to the surface of the above-mentioned layer (b) and then a polypropylene film having a thickness of 60 μm was laminated thereon to fabricate a gas barrier multilayer film.

Example 27

First, a urethane-based adhesive (available from MITSUI TAKEDA CHEMICALS, INC., Takelac A-620, and hardener: Takenate A-65) was applied to the corona-treated side of a biaxially oriented polyester film (support) having a thickness of 12 μm using a mayer bar so as to make the thickness 0.1 μm and the resulting material was dried at a temperature of 90° C. for 30 seconds to form an anchor coat layer. Then, a gas barrier multilayer film was fabricated similarly to Example 26 except that the coating solution (A) was applied to the surface of the above-described anchor coat layer.

Examples 28 and 29

Each gas barrier multilayer film was fabricated similarly to Example 26 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) obtained in Example 2 (Example 28), or the coating solution (A) obtained in Example 3 (Example 29) was used.

Example 30

A gas barrier multilayer film was fabricated similarly to Example 26 except that a biaxially oriented polyamide film having a thickness of 15 μm was used in place of the biaxially oriented polyester film having a thickness of 12 μm.

Example 31

First, a urethane-based adhesive (available from MITSUI TAKEDA CHEMICALS, INC., Takelac A-620, hardener: Takenate A-65) was applied to the corona-treated side of a biaxially oriented polypropylene film (support) having a thickness of 20 μm using a mayer bar so as to make the thickness 0.1 μm and the resulting material was dried at a temperature of 90° C. for 30 seconds to form an anchor coat layer. Then, a gas barrier multilayer film was fabricated similarly to Example 26 except that the coating solution (A) was applied to the surface of the above-described anchor coat layer.

Example 32

A gas barrier multilayer film was fabricated similarly to Example 26 except that the coating solution (A) obtained in Example 4 was used in place of the coating solution (A) obtained in Example 1.

Comparative Examples 23 to 27

Each gas barrier multilayer film for comparison was fabricated similarly to Example 26 except that, in place of the coating solution (A) obtained in Example 1, the coating solution (A) used in Comparative Example 3 (Comparative Example 23), the coating solution (A) used in Comparative Example 4 (Comparative Example 24), the coating solution (A) used in Comparative Example 5 (Comparative Example 25), the coating solution (A) used in Comparative Example 6 (Comparative Example 26), or the coating solution (A) used in Comparative Example 7 (Comparative Example 27) was used.

(iv) Measurement of Oxygen Permeability Under High Moisture Atmosphere

Each resultant gas barrier multilayer film was taken as a film sample and subjected to oxygen permeability measurement (temperature of 30° C. and humidity of 80% RH) in a high moisture atmosphere. In other words, the oxygen permeability of a film sample was measured at a temperature of 30° C. and a relative humidity of 80% (RH) on both sides using an oxygen permeation tester (OX-TRAN2/20; available from MOCON Inc.). In addition, the units are cm³ (STP)/m²·day·MPa. The results obtained and the compositions of the supports and the coating solution (A) used in the Examples and Comparative Examples are listed in Table 6.

TABLE 6 Composition of coating solution (A) (*11) Number Gas barrier average multilayer film Composition of support molecular Oxygen permeability Anchor weight of Alkali Chemical Multivalent Chemical at a temperature of coat polyacrylic metal equivalent metal equivalent 30° C. and 80% Material layer acid compound (*12) compound (*12) RH (cm³ (STP)/m² · day · MPa) Example 26 Biaxially None 200,000 Sodium 0.10 Zinc oxide 0.30 22 oriented hydroxide polyester Example 27 Biaxially Present 200,000 Sodium 0.10 Zinc oxide 0.30 20 oriented hydroxide polyester Example 28 Biaxially None 50,000 Sodium 0.10 Zinc oxide 0.30 23 oriented hydroxide polyester Example 29 Biaxially None 200,000 Sodium 0.05 Calcium 0.10 29 oriented hydroxide chloride polyester Example 30 Biaxially None 200,000 Sodium 0.10 Zinc oxide 0.30 31 oriented hydroxide polyamide Example 31 Biaxially Present 200,000 Sodium 0.10 Zinc oxide 0.30 38 oriented hydroxide polypropylene Example 32 Biaxially None 200,000 Sodium 0.10 Calcium 0.40 18 oriented hydroxide hydroxide polyester Comparative Biaxially None 200,000 — — — — 270 Example 23 oriented polyester Comparative Biaxially None 200,000 Sodium 0.03 — — 280 Example 24 oriented hydroxide polyester Comparative Biaxially None 200,000 — — Zinc oxide 0.03 250 Example 25 oriented polyester Comparative Biaxially None 200,000 — — Calcium 0.03 260 Example 26 oriented hydroxide polyester Comparative Biaxially None 25,000 Sodium 0.05 Zinc oxide 0.15 170 Example 27 oriented hydroxide polyester (*11) The amount of polyacrylic acid in the coating solution (A) is 5 parts by weight relative to 100 parts by weight of water. (*12) The chemical equivalent indicates a chemical equivalent of a metal compound relative to the carboxyl group of polyacrylic acid.

As apparent from the results indicated in Table 6, it is verified that a gas barrier multilayer film of the present invention, even before crosslinking caused by the multivalent metal compound progresses, i.e., even before processing (sterilization), such as boiling and retort sterilization, under high temperature hot water conditions is applied, have excellent oxygen barrier properties in a high moisture atmosphere.

<Package>

Example 33

Polypropylene film sides of the gas barrier multilayer film obtained in Example 27 were heat-sealed to each other with an impulse sealer to fabricate a three side sealed pouch of a size 25 cm×15 cm. Thereafter, 200 g of water was filled in this pouch, and then air-tightly sealed to obtain a package.

Next, the resultant package was immersed in water of 20° C. for 24 hours and the appearance and the oxygen permeability of the package after immersion treatment were evaluated or measured. In other words, when the appearance of the package after immersion treatment was visually evaluated, the transparency of the package was good. In addition, a part of the package after immersion treatment to which heat was not applied by the impulse sealer was excised. The part was taken as a sample and its oxygen permeability was measured, with the oxygen permeability being 14 cm³ (STP)/m²·day·MPa. The oxygen permeability was measured under a condition of a temperature of 30° C. and a relative humidity (RH) of 0% on the both side using an oxygen permeation tester (available from MOCON Inc: OX-TRAN2/20).

Additionally, the resulting package was subjected to sterilization using an autoclave under a condition of a temperature of 120° C. and a pressure of 2.5 Kg/cm² for 30 minutes and then the appearance and the oxygen permeability of the package after sterilization were evaluated or measured by the same method as the above. As a result, the transparency of the package after sterilization was good. Moreover, the oxygen permeability of the sample that excised from the package after sterilization was 8 cm³ (STP)/m²·day·MPa.

As apparent from the results described above, according to the present invention, it was verified that even when a packaging material is exposed to cold water of 30° C. or less before sterilization, the occurrence of whitening and deterioration of transparency is prevented and that a packaging material that is suitable for heat sterilization packaging application can be obtained.

Industrial Applicability

As described above, the present invention makes it possible to provide a coating solution for obtaining a packaging material in which whitening can be sufficiently prevented, and also which is excellent in gas barrier properties and transparency, even when the material is exposed to cold water of 30° C., for example, in the case where the packaging material is used for a heat sterilization packaging application or the like. The present invention also makes it possible to provide a gas barrier film, a gas barrier laminate, and a gas barrier multilayer film, using the coating solution, as well as their manufacturing methods.

Consequently, the present invention is useful as a technique related to packaging materials of foods, beverages, chemicals, medicines and precision metal components such as electronic components, which tend to degrade due to the effect of oxygen or the like, and packaging materials of articles that need processing (heat sterilization) such as boiling and retort sterilization, under high-temperature hot water conditions, and particularly useful as a technique related to a packaging material of heat sterilization packaging applications. 

The invention claimed is:
 1. A coating solution consisting of: a first solvent selected from the group consisting of water, methyl alcohol, ethyl alcohol, isopropyl alcohol and mixtures thereof;
 0. 1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, wherein the polycarboxylic acid-based polymer is a (co)polymer of α,β-monoethylenically unsaturated carboxylic acids; 0.01 to 0.35 chemical equivalent of a hydroxide of an alkali metal relative to an amount of carboxyl group in the polycarboxylic acid-based polymer; a multivalent metal compound selected from the group consisting of calcium hydroxide of 0.05 to 0.75 chemical equivalent relative to the amount of the carboxyl group and zinc oxide of 0.05 to 0.50 chemical equivalent relative to the amount of the carboxyl group; an optional additional polymer; and an optional inorganic layered compound, wherein a number average molecular weight of the polycarboxylic acid-based polymer is in a range of 40,000 to 10,000,000.
 2. A gas barrier film comprising: a layer (a) formed from a coating solution (A) which consists of a first solvent selected from the group consisting of water, methyl alcohol, ethyl alcohol, isopropyl alcohol and mixtures thereof, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, wherein the polycarboxylic acid-based polymer is a (co)polymer of α,β-monoethylenically unsaturated carboxylic acids, 0.01 to 0.35 chemical equivalent of a hydroxide of an alkali metal relative to an amount of carboxyl group in the polycarboxylic acid-based polymer, and a multivalent metal compound selected from the group consisting of calcium hydroxide of 0.05 to 0.75 chemical equivalent relative to the amount of the carboxyl group and zinc oxide of 0.05 to 0.50 chemical equivalent relative to the amount of the carboxyl group, an optional additional polymer, and an optional inorganic layered compound, and in which a number average molecular weight of the polycarboxylic acid-based polymer is in a range of 40,000 to 10,000,000; and a support, the gas barrier film having the layer (a) formed from the coating solution (A) on at least one side of the support.
 3. A gas barrier laminate comprising: a layer (a) formed from a coating solution (A) which consists of a first solvent selected from the group consisting of water, methyl alcohol, ethyl alcohol, isopropyl alcohol and mixtures thereof, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, wherein the polycarboxylic acid-based polymer is a (co)polymer of α,β-monoethylenically unsaturated carboxylic acids, 0.01 to 0.35 chemical equivalent of a hydroxide of an alkali metal relative to an amount of carboxyl group in the polycarboxylic acid-based polymer, and a multivalent metal compound selected from the group consisting of calcium hydroxide of 0.05 to 0.75 chemical equivalent relative to the amount of the carboxyl group and zinc oxide of 0.05 to 0.50 chemical equivalent relative to the amount of the carboxyl group, an optional additional polymer, and an optional inorganic layered compound, and in which a number average molecular weight of the polycarboxylic acid-based polymer is in a range of 40,000 to 10,000,000; a layer (b) formed from a coating solution (B) containing the multivalent metal compound and a second solvent; and a support, the gas barrier laminate having, on at least one side of the support, at least one lamination unit in which the layer (a) formed from the coating solution (A) and the layer (b) formed from the coating solution (B) are adjacent to each other.
 4. A gas barrier multilayer film comprising: the gas barrier laminate according to claim 3; and a plastic film laminated on at least one side of the gas barrier laminate.
 5. A packaging material comprising: the gas barrier laminate according to claim
 3. 6. A packaging comprising: the gas barrier laminate according to claim
 3. 7. A method of manufacturing a gas barrier film comprising: applying, to at least one side of a support, a coating solution (A) which consists of a first solvent selected from the group consisting of water, methyl alcohol, ethyl alcohol, isopropyl alcohol and mixtures thereof, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, wherein the polycarboxylic acid-based polymer is a (co)polymer of α,β-monoethylenically unsaturated carboxylic acids, 0.01 to 0.35 chemical equivalent of a hydroxide of an alkali metal relative to an amount of carboxyl group in the polycarboxylic acid-based polymer, and a multivalent metal compound selected from the group consisting of calcium hydroxide of 0.05 to 0.75 chemical equivalent relative to the amount of the carboxyl group and zinc oxide of 0.05 to 0.50 chemical equivalent relative to the amount of the carboxyl group, an optional additional polymer, and an optional inorganic layered compound, and in which a number average molecular weight of the polycarboxylic acid-based polymer is in a range of 40,000 to 10,000,000, followed by drying to obtain a gas barrier film having the layer (a) formed from the coating solution (A).
 8. A method of manufacturing a gas barrier laminate, comprising: applying, to at least one side of a support, a coating solution (A) which consists of a first solvent selected from the group consisting of water, methyl alcohol, ethyl alcohol, isopropyl alcohol and mixtures thereof, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, wherein the polycarboxylic acid-based polymer is a (co)polymer of α,β-monoethylenically unsaturated carboxylic acids, 0.01 to 0.35 chemical equivalent of a hydroxide of an alkali metal relative to an amount of carboxyl group in the polycarboxylic acid-based polymer and, a multivalent metal compound selected from the group consisting of calcium hydroxide of 0.05 to 0.75 chemical equivalent relative to the amount of the carboxyl group and zinc oxide of 0.05 to 0.50 chemical equivalent relative to the amount of the carboxyl group, an optional additional polymer, and an optional inorganic layered compound, and in which a number average molecular weight of the polycarboxylic acid-based polymer is in a range of 40,000 to 10,000,000 and a coating solution (B) which contains the multivalent metal compound and a second solvent, followed by drying to obtain a gas barrier laminate having at least one lamination unit in which the layer (a) formed from the coating solution (A) and the layer (b) formed from the coating solution (B) are adjacent to each other.
 9. A method of manufacturing a gas barrier multilayer film, comprising: applying, to at least one side of a support, a coating solution (A) which consists of a first solvent selected from the group consisting of water, methyl alcohol, ethyl alcohol, isopropyl alcohol and mixtures thereof, 0.1 to 30 parts by weight of a polycarboxylic acid-based polymer relative to 100 parts by weight of the solvent, wherein the polycarboxylic acid-based polymer is a (co)polymer of α,β-monoethylenically unsaturated carboxylic acids, 0.01 to 0.35 chemical equivalent of a hydroxide of an alkali metal relative to an amount of carboxyl group in the polycarboxylic acid-based polymer, and a multivalent metal compound selected from the group consisting of calcium hydroxide of 0.05 to 0.75 chemical equivalent relative to the amount of the carboxyl group and zinc oxide of 0.05 to 0.50 chemical equivalent relative to the amount of the carboxyl group, an optional additional polymer, and an optional inorganic layered compound, and in which a number average molecular weight of the polycarboxylic acid-based polymer is in a range of 40,000 to 10,000,000 and a coating solution (B) which contains the multivalent metal compound and the second solvent, followed by drying to obtain a gas barrier laminate; and laminating a plastic film on at least one side of the barrier laminate to obtain a gas barrier multilayer film. 